It is ordinarily known that odor characteristics of a perfume largely depend on a compound having an aroma and kinds of a slight amount of impurities contained therein or additives added separately. Changes of the formulation or composition of the substances may produce a novel aroma as a perfume or may produce an unpleasant smell. Therefore, the quality of the compound having an odor and the kind and compositional ratio of the minor component contained therein are substantially important for determining the value of the perfume product. Accordingly, a purification step is very important to obtain a perfume compound generating an aroma, on producing a perfume product.
As a purification method of a perfume compound, separation of impurities by distillation or cryogenic separation, removal of impurities by adsorption, etc. have been known. However, special equipments may be often required in the method other than distillation, and for example, the adsorption method involves some problems, such as quality deterioration caused by elution of the adsorbent itself to the product. Otherwise, the purification by distillation can be easily carried out, but in the case where a target perfume compound is a high boiling point fraction, it is necessary to discard a large amount of the initial distillation fraction for preventing low boiling point impurities from being mixed therein, thereby providing a problem of decreasing the yield. Furthermore, under the heating condition, a prolonged period of distillation causes a decomposition of the perfume compound, and side reactions increasing impurities, and the impurities are mixed in the target product to finally provide a problem of deteriorating the quality and the aroma.
2-Methyl-3-(3,4-methylenedioxyphenyl)propanal is an ingredient of marine perfume that is widely used in an ordinary perfumery and cosmetics, such as perfume (eau de cologne), soap, shampoo, conditioner, detergent, cosmetics, perfume spray, fragrance material, etc. (disclosed, for example, in Non-patent Document 1).
As a method for producing 2-methyl-3-(3,4-methylenedioxyphenyl)propanal, such methods have been known as a method of carrying out finally hydrogenation reaction of 2-methyl-3-(3,4-methylenedioxyphenyl)-2-propenal via heliotropin from obtained safrole purified from sassafras oil (disclosed, for example, in Patent Document 1), a method of producing from 1-acetoxy-2-methyl-3-(3,4-methylenedioxyphenyl)-1-propene (disclosed, for example, in Patent Documents 2 and 3), and so on. Patent Documents 4 to 7 disclose a method of producing 2-methyl-3-(3,4-methylenedioxyphenyl)propanal from 1,2-methylenedioxybenzene as a starting material.
Patent Document 2 discloses that 1,2-methylenedioxybenzene and 2-methyl-3,3-diacetoxypropene are reacted to synthesize 1-acetoxy-2-methyl-3-(3,4-methylenedioxyphenyl)-1-propene, and then the compound is hydrolyzed to provide 2-methyl-3-(3,4-methylenedioxyphenyl)propanal as the target product. However, there is no description regarding to impurities and aroma, which are important for a perfume product, of the obtained 2-methyl-3-(3,4-methylenedioxyphenyl)propanal.    [Non-patent Document 1] Angew. Chem. Int. Ed., vol.39(17), p.2980 (2000)    [Patent Document 1] U.S. Pat. No. 3,008,968    [Patent Document 2] JP-A-57-45124    [Patent Document 3] JP-A-2006-104151    [Patent Document 4] JP-A-55-141437    [Patent Document 5] JP-A-2005-239619    [Patent Document 6] WO 2004/054997    [Patent Document 7] WO 2006/120639